The following U.S. military report covers two types of Japanese high-explosive incendiary
bombs designed for aerial bursts. The report
was originally published in Tactical and Technical Trends,
No. 47, June 1, 1944.

[DISCLAIMER: The following text is taken from the U.S. War Department
publication Tactical and Technical Trends. As with all wartime
intelligence information, data may be incomplete or inaccurate. No
attempt has been made to update or correct the text. Any views or
opinions expressed do not necessarily represent those of the website.]

JAPANESE
AERIAL BURST BOMBS

A British source states that as of the latter part of January 1944 there were
two types of Japanese high explosive, incendiary bombs known to be intended to
give aerial bursts.

* * *

a. 32-Kg Bomb

The most commonly used type appears to be the 32 kilogram (70 pound) Model 99
high explosive incendiary bomb. This bomb is equipped with an impact
nose fuze and a mechanical time tail fuze. The tail contains 3-1/2 pounds of high
explosive, and the body contains 198 incendiary pellets of steel filled with
phosphorus. The angled tail fins causes the bomb to spin in the air. On explosion, the
incendiary pellets are shot down in the form of a cone with an estimated
danger radius of 50 to 75 yards. The fragmentation effect will probably not extend
beyond 75 yards, but the incendiary effect will continue below the point of
bursts, depending on the time required for the pellets to burn.

b. 250-Kg Bomb

This bomb (see Tactical and Technical Trends No. 36, p. 39) is a
550 pound high explosive incendiary bomb. It is equipped with impact nose
fuze and a time fuze in the tail. This bomb contains 75 pounds of high explosive
and 756 incendiary fragments. The angled tail fins cause the bomb to spin in
the air, and on explosion, the fragments are sprayed conically downwards. The
fragments are scattered over a 175-yard radius when the air burst
occurs 100 ft above the ground and the incendiary action continues for 20 seconds.

c. Time Fuze

The aerial burst fuzes are all mechanical time fuzes. Settings can be
made in the airplane. These fuzes are not armed until the bomb attains a speed
of 1,000 rpm. This requires a drop of 3,000 feet for the 250-kg bomb, and this
bomb must therefore be dropped at least that distance before it will burst. The
32-kg bomb probably requires a similar drop. They may be set to drop much
greater distances before bursting.

d. Bomb Clusters

Japanese sources indicate that cluster bombs may be used against either
airborne or grounded aircraft. There are two types. A two pound bomb is packed
40 to a cluster, and the more common 2/3 pound is packed 76 to a cluster. The
cluster opens shortly after leaving the releasing plane, which, it is believed, makes
the drop a few hundred feet above the target. The individual bombs scatter. Explosions
occur only as separate bombs hit targets. They are a hollow-charge
type. A penetration of several inches of steel is possible for such bomb blast in
the limited area directly in front of the bomb nose. A further effect is described
as similar to the explosion of a 40-mm AA shell, excluding fragmentation.